This invention relates to a device for supporting a hydraulic or pneumatic impact tool or breaker, used widely for crushing and demolition work at quarries and civil engineering and construction sites, on the tip of an arm of a power shovel or the like.
As shown in FIG. 1, such an impact tool 10 is mounted on the tip of an arm 2 of a self-propelled carriage 13 such as a power shovel. During use, it tends to be violently vibrated up and down. The vibration of the impact tool 10 will have a bad influence on the carriage 13 or the operator if it is transmitted directly to them.
FIG. 7 shows a prior art arrangement for preventing the vibration of the impact tool 1 from being transmitted to the carriage. In this arrangement, vibration-proof support members 7 each comprising two support fittings 4, 5 and a vibration-proof rubber member 6 sandwiched therebetween are each disposed between a respective side of an impact tool 1 and a bracket 3 having a pair of side plates and mounted on the tip of the arm 2 of a power shovel.
In order to efficiently crush rocks and concrete structures, the tip of the chisel 8 of the impact tool 1 has to be pressed hard against the object to be crushed when actuating the impact tool 1.
When the tip of the chisel 8 of the impact tool 2 is pressed hard against the object to be crushed by actuating a boom 14 and the arm 2, the vibration-proof rubber members tend to be subjected to an excessive shearing force. Especially if the axis of the impact tool 1 is not perpendicular but inclined with respect to the object to crushed as shown in FIG. 1, the impact tool 1 has a tendency to pivot in the bracket 15 about the tip of the chisel in the direction shown by arrow B. Thus, a large turning force (torsional force) always acts on the vibration-proof support members 7 supporting the impact tool 1 and the brackets 3. This will accelerate the fatigue of the vibration-proof rubber members 6 of the support members 7. Also, if the impact tool 1 is pressed hard against the object to be crushed, it may move in the direction A with respect to the brackets 3. If this happens, the vibration-proof rubber members may be broken due to a large shearing force that acts thereon.